Method and apparatus for separating tobacco leaf laminae from tobacco ribs



Nov. 12, 1968 w. WOCHNOWSKI 3,410,280

METHOD AND APPARATUS FOR SEPARATING TOBACCO LEAF LAMINAE FROM TOBACCO RIBS Filed Sept. 2, 1966 2 Sheets-Sheet 1 44 A: 1Q L? 38 45 H HLW' H I J INVENTOR.

U0 410M0 l/ocl mmkd BY Nov. 12, 1968 w. WOCHNOWSKI 3,410,280

METHOD AND APPARATUS FOR SEPARATING TOBACCO LEAF LAMINAE FROM TOBACCO RIBS 2 Sheets-Sheet 2 Filed Sept.

Ff Fig.4aFig.4b

IN VENTOR. 4/5 fdgmq 4/ 9 11 a. B)

United States Patent 3,410,280 METHOD AND APPARATUS FOR SEPARATING TOBACCO LEAF LAMINAE FROM TOBACCO RIBS Waldemar Wochnowski, Hamburg, Germany, assignor to Hauni-Werke Korber & Co. KG., Hamburg-Bergedorf, Germany Filed Sept. 2, 1966, Ser. No. 576,961 Claims priority, application Germany, Sept. 3, 1965,

13 Claims. Ci. 131-146) ABSTRACT OF THE DISCLOSURE A method and apparatus for separating laminae from tobacco leaves wherein the leaves are destalked to form a mixture which contains free laminae and ribs. The major percentage of laminae is separated from the mixture so that the remainder forms a secondary mlxture. The major percentage of the remaining laminae is separated from the secondary mixture and the remainder of the secondary mixture is mixed with a third mixture.

The present invention relates to a method and apparatus for comminuting tobacco leaves and for separating tobacco leaf laminae from ribs.

Tobacco leaf laminae which are segregated from a mixture containing laminae and ribs should contain none or only a small percentage of ribs, usually not more than between 0.3 and 1 percent. In accordance with the presently prevailing practice, whole tobacco leaves are comminuted in a destalking machine and the resulting mixture of laminae and ribs is thereupon passed through a pneumatic separator which segregates laminae so that the remainder of the mixture contains mainly ribs. In order to guarantee that the mass of segregated laminae will contai no ribs at all or a negligible percentage of ribs, the flow of gaseous carrier in the separator is selected in such a way that the segregation of laminae from the mixture is only partial, i.e., that a substantial percentage of laminae remains intermingled with the ribs which descend by gravity and leave the gaseous carrier. The remainder of the mixture which by now contains a relatively high percentage of ribs is then subjected to a series of additional separating actions to segregate some or all of the remaining laminae. However, such separation of laminae from a mass or stream which contains mainly ribs presents serious problems because it is a well-known fact that the segregation of laminae in a pneumatic separator is more difficult if the mixture from which the laminae are to be segregated contains a relatively high percentage of heavier particles which tend to descend by gravity and entrain the lighter laminae. During secondary destalking, laminae which are mixed with pure ribs and/ or with ribs still carrying fragments of laminae are broken up into small fragments which is undesirable because the lighter fraction should contain a very small percentage of laminae with a size of less than inch. As a rule, the mass of laminae should contain a high percentage of particles with a size of 1 inch or more.

Accordingly, it is an important object of the present invention to provide a novel method and apparatus for destalking tobacco leaves and for thereupon segregating tobacco leaf laminae from the resulting mixture in such a way that the laminae are not broken up into small fragments and that the segregation can be carried out with a high degree of elficiency.

Another object of the invention is to provide a method and apparatus of the just outlined characteristics which "Ice may utilize one or more conventional destalking machines and wherein the segregation of laminae from ribs can be carried out in a small area and will result in recovery of a surprisingly high percentage of large laminae.

A further object of the invention is to provide a novel system of separators which may be utilized in an apparatus of the above outlined character.

An additional object of the invention is to provide an apparatus with two or more destalking machines and two or more groups of pneumatic separators, and to construct and assemble the apparatus in such a way that all or nearly all laminae which were separated from ribs in the first destalking machine are removed from the mixture before the remainder of the mixture enters the next destalking machine to thus insure that free laminae which are already separated from ribs need not pass through additional destalking machines which would be likely to comminute such laminae into small fragments.

The method of my invention is used to separate tobacco leaf laminae from ribs and comprises the steps of destalking tobacco leaves to form a primary mixture containing separated or free laminae and lighter and heavier ribs some of which still carry fragments of laminae, separating from the primary mixture the major percentage of laminae whereby the remainder of the primary mixture forms a secondary mixture containing a relatively heavy concentration of ribs and the remaining free laminae, separating from the secondary mixture the major percentage of free laminae and at least some (preferably lighter) ribs to form a third mixture, separating free laminae from the third mixture, and mixing the remainder of the secondary and third mixtures to form a fourth mixture. The remainder of the secondary mixture consists of the heavier fraction of the primary mixture and is free of separated laminae.

Since some of the ribs which are separated from laminae in the destalking step still carry fragments of laminae, the fourth mixture is preferably subjected to further destalking to separate from ribs at least some fragments of laminae. The resulting mixture of free laminae and ribs is then subjected to one or more further separating actions to segregate free laminae.

The aforementioned third mixture may be formed subsequent to a single destalking treatment and/or subsequent to two or more successive destalking treatments. A very important advantage of the step of forming such third mixture (which contains laminae and some lighter ribs) is that the segregation of laminae from a mixture containing a low concentration of heavier particles is much more convenient than segregation of laminae from a mixture which contains a high concentration of heavier particles. By the simple expedient of forming a third mixture which contains lighter and heavier particles, the segregation of lighter particles (namely, pure laminae) is much simpler and can be carried out in a simple separator wherein the laminae are not likely to adhere to or to be otherwise entrained by ribs.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a diagram showing the main components of a four-stage apparatus which embodies by invention;

FIG. 2 is a diagram showing certain components of a slightly modified multi-stage apparatus;

FIG. 3 is a diagram of the structure shown in FIGS. 3a and 3b;

FIG. 3a is a larger-scale side elevational view of the left-hand half of the apparatus shown in FIG. 1;

FIG. 3b is a similar side elev-ational view and illustrates on a larger scale the right-hand half of the apparatus shown in FIG. 1;

FIG. 4 is a diagram of the structure shown in FIGS. 4a and 4b;

FIG, 4a is a top plan view of the structure shown in FIG. 3a; and

FIG. 4b is a top plan view of the structure shown in FIG. 3b.

Referring first to the diagram of FIG. 1, there is shown a four-stage apparatus for destalking tobacco leaves and for segregating tobacco leaf laminae from ribs. A conveyor system 2 advances whole tobacco leaves and mixtures of various concentrations of free laminae with ribs through the four stages of the apparatus. The first stage comprises a destalking machine 4 which receives a continuous stream of whole tobacco leaves and breaks up such leaves to form a primary mixture containing fully separated or free laminate and lighter and heavier ribs. However, at least some of the ribs still carry fragments of laminae. The first stage also comprises two serially arranged primary separators 6 and 8. The second stage comprises a destalking machine 12 and two separators 14, 16. The third and fourth stages respectively comprise destalking machines 18, 22 and primary separators 20, 24.

In accordance with an important feature of my invention, the first stage comprises a secondary separator 10 which is connected in series with the second primary separator 8, and an additional separator 28 connected in series with the secondary separator 10.

The arrows 34, 36, 38, 40, 42, 44, 46 respectively denote the outlets or material discharging means of separators 6, 8, 28, 14, 16, 20, 24 which discharge streams of free laminae into a collecting pipe 48. The separator 6 segregates a substantial percentage of free laminae from the primary mixture issuing from the destalking machine 4, and its outlet 34 discharges such laminae into the collecting pipe 48. The remainder of the primary mixture still contains a considerable amount of free laminae a substantial percentage of which is segregated in the separator 8 whose outlet 36 delivers segregated laminae into the pipe 48. The secondary mixture constituting the remainder of the primary mixture and delivered by the conveyor system 2 into the secondary separator 10 contains a much lower percentage of free laminae, and this separator 10 is arranged to segregate from the secondary mixture issuing from the separator 8 all of the free laminae and a small percentage of lighter ribs which form with such free laminae a third mixture passing through the outlet 26 and into the additional separator 28 which is arranged to segregate free laminae from lighter ribs and to admit laminae into the collecting pipe 48 via outlet 38. A second outlet 30 of the separator 28 delivers lighter ribs into the outlet 32 of the secondary separator 10 wherein such lighter ribs merge with the remainder of the secondary mixture which was admitted to the separator 10. Such remainder of the secondary mixture consists of heavier and lighter ribs. The outlet 32 forms part of the conveyor system 2 and delivers the resulting fourth mixture of lighter and heavier ribs toward the. destalking machine 12 of the second stage. The machine 12 separates lighter and heavier ribs from fragments of laminae which were not separated in the destalking machine 4, and the resulting fifth mixture of lighter and heavier ribs (some of which still carry fragments of laminae), free fragments of laminae, and some laminae which were separated in the machine 4 but were not segregated from ribs in the separators 6, 8, 10 and 28, is then caused to pass through the separators 14, 16 which segregate laminae and fragmen-ts of laminae to deliver such material into the pipe 48 via outlets 40, 42.

The remainder of the mixture which was admitted to the separator 16 by now contains a very high concentration of ribs, some free laminae and fragments of laminae, and also some fragments which still adhere to the ribs. This remainder is admitted into the destalking machine 18 of the third stage which separates additional fragments from their ribs and admits the resulting mixture into the separator 20 which segregates free laminae and free fragments of laminae and admits them to pipe 48 via outlet 44, The treatment in the fourth stage is analogous with the exception that the mixture admitted into the destalking machine 22 contains a very low percentage of laminae and fragments of laminae. The machine 22 separates the remaining fragments from lighter and heavier ribs and forms a mixture which enters the separator 24. The outlet 46 admits segregated laminae into the pipe 48 and the conveyor system 2 advances from the second outlet of the separator 24 a stream of substantially pure ribs.

The conveyor system 2 may include mechanical and/ or pneumatic components. The separators are preferably pneumatic separators wherein the lighter particles travel concurrent with air and the heavier particles travel countercurrent in that they descend :by gravity and leave the gaseous carrier. In FIG. 1, the outlets 34, 36, 26, 38, 40, 42, 44, 46 convey lighter ribs (outlet 26) and laminae concurrent with air, but the outlets 30, 32 convey material in a direction countercurrent to the flow of air which is utilized to bring about segregation.

In destalking of tobacco leaves and in segregation of laminae from the resulting primary mixture, it is customary to refer to the following types of materials: Whole tobacco leaves fed to the machine 4 are comminuted to form a primary mixture consisting of clean ribs (without fragments of laminae), free laminae which are fully separated from ribs, and ribs which still carry fragments of laminae. The heavier fraction of such primary mixture includes clean ribs and ribs with fragments of laminae. The lighter fraction consists of free laminae and is admitted into the pipe 48. The material issuing from the second outlet of the separator 6 and entering the inlet of the separator 8 contains a relatively high percentage of heavier fraction, and the material entering the separator 10 contains a still higher concentration of the heavier fraction. The material leaving the separator 10 via outlet 26 contains heavier particles of the lighter fraction and lighter particles of the heavier fraction, i.e., the strength of the ascending current of gaseous carrier in the separator 10 is selected in such a way that this current entrains all heavier laminae and some of the lighter ribs while the heavier ribs leave the gaseous carrier by gravity and are evacuated through the outlet 32 to be introduced into the destalking machine 12.

The function of the separator 10 is to segregate from the material leaving the second outlet of the separator 8 a mixture of heavy free laminae and lighter ribs. Such mixture is readily separable into ribs and laminae, namely, with greater facility than if the laminae were to be segregated from a mass which contains a much higher percentage of heavier fraction. This insures that nearly all of the free laminae (separated from ribs in the machine 4) are segregated from the primary mixture before the remainder of the primary mixture enters the second destalking machine 12 which would reduce the size of free laminae. Therefore, the apparatus of FIG. 1 separates an unexpectedly high percentage of relatively large laminae with a size of 1 inch or more.

The efficiency of pneumatic separators with high output is considerably less than the efliciency of pneumatic separators with low output. This is due to the fact that the flow of gaseous carrier must be uniform in each zone of the cross-sectional area of the separator. This can be achieved only if the cross-sectional area of the separator is small. In a modern separating apparatus, high outputs can be achieved by feeding large quantities of mixture into the gaseous carrier which results in less staisfactory segregation of laminae. In accordance with my present invention the separator diverts from the main body of the secondary stream a relatively small quantity of material, namely, such laminae which are hard to segregate from the high concentration of ribs. This small quantity of material which leaves the separator 10 through the outlet 26 can be readily and effectively broken up into laminae and ribs because the percentage of heavier fraction is low.

The segregation of laminae from the mixture entering the separator 28 is carried out in an ascending current of air which is best suited for such operation because it can segregate laminae from a mixture wherein the weight of ribs need not be substantially greater than the weight of laminae. Many of the laminae in the mixture entering the separator 28 are large because such large laminae are often draped around the ribs and cannot be segregated in the separator 6 or 8 each of which should segregate only pure laminar stock. Were the strength of the air current in the separator 6 and/or 8 increased to such an extent that the current would entrain all of thelaminae, such current would invariably segregate a considerable percentage of light ribs whose weight is not substantially above the weight of large laminae.

Repeated segregation of free laminae from the primary mixture (separators 6 and 8) prior to entry into the secondary separator 10 is advisable because the latter is then more likely to segregate such free laminae which are more diflicult to separate without simultaneous segregation of some ribs. Thus, the results are more satisfactory if the secondary separator 10 receives a mixture having a high concentration of heavier fraction.

The diagram of FIG. 2 illustrates certain details of a modified multi-stage apparatus. The secondary separator 116 is installed in the second stage and is analogous to the separator 10 of FIG. 1, i.e., it breaks up the mixture issuing from the primary separator 114 of the second stage into a mixture containing laminae and lighter ribs and a stream of heavier ribs which are admitted into the destalking machine 118 of the third stage. The outlet 142 delivers the mixture of laminae and lighter ribs into an additional separator 128 which segregates free laminae and admits then to the collecting pipe 148 via outlet 138. The second outlet 130 of the separator 128 admits lighter ribs into the second outlet 132 of the separator 116 wherein the lighter ribs merge with heavier ribs and the resulting mixture enters the destalking machine 118.

The apparatus of FIG. 2 may comprise all components of the apparatus shown in FIG. 1 plus the separator 128. Thus, the separator 28 may be replaced by or is provided in addition to the separator 128. The conveyor system 102 performs the same function as in the apparatus of FIG. 1. The first and fourth stages of this modified apparatus are not shown in FIG. 2. The second stage comprises the aforementioned separators 114, 116, 128 with outlets 140, 142, 132, 138, 130, and a destalking machine 112.

FIGS. 3a, 3b, 4a and 4b illustrate in greater detail the construction of the apparatus which was shortly described in connection with the diagram of FIG. 1. FIG. 3b shows that the outlet 26 of the secondary separator 10 is connected with an air lock 50 having a discharge pipe 52 located at a level above a rapidly traveling conveyor belt 54. This belt 54 serves to deliver the third mixture consisting of free laminae and lighter ribs into the inlet of the additional separator 28. The outlet 30 of the additional separator 28 is located at the latters lower end and discharges lighter ribs onto a conveyor belt 32 which constitutes the second outlet of the separator 10 and delivers lighter and heavier ribs to an elevator 64 serving to feed such ribs into the destalking machine 12 of the second stage. The separators 6, 8, 14, 16, 20, 24 may be of the type disclosed in German Patent No. 1,185,100 and their exact construction forms no part of the present invention.

FIGS. 3b and 4b show that the separator 6 comprises two branch conduits 56 which are united into a single outlet 34. The conveyor system 2 is composed of mechanical and pneumatic components including an elevator 58 which admits a continuous and uniform stream of whole tobacco leaves into the destalking machine 4, a hopper 60 which receives the primary mixture from the machine 4, a pneumatic conveyor duct 62 which delivers the primary mixture into the separator 6, the elevator 64 which admits the mixture of heavier and lighter ribs (coming from the outlets 30, 32) into the destalking machine 12, an elevator 66 which admits material issuing from the separator 16 (lighter and heavier ribs) into the destalking machine 18, a hopper 68 which feeds material from the machine 12 into a pneumatic conveyor duct 70 discharging into the separator 14, a hopper 72 which feeds material from the machine 18 into a pneumatic conveyor duct 74 discharging into the separator 20, hoppers 76, 78, which receive material from the separators 6, 8, 14, pneumatic conveyor ducts 82, 84, 86 which deliver material to the separators 8, 10, 16, a conveyor belt 88 which delivers material from the separator 20 to the destalking machine 22, and a conveyor belt 90 for delivering material from the machine 22 to the separator 24.

The placing of the belt 32 directly below the outlet 30 of the additional separator 28 reduces the space requirements and cost of the conveyor system 2. Also, such mounting of the belt 32 insures that lighter rigs leaving the separator 28 are mixed with the remainder of the secondary stream which is conveyed from the separator 10 into the destalking machine 12.

The efiiciency of the separator 28 (as regards the segregation of laminae from lighter ribs) is improved by the provision of the rapidly travelling belt 54 which propels the mixture fed by the pipe 52 at a high speed and across the full width of the separator 28. This insures uniform distribution of the mixture in the ascending gaseou 1' carrier.

The operation of the apparatus shown in FIGS. 3a, 3b,

4a, and 4b will now be described in full detail and by giving actual figures regarding the weight of various fractions. Such figures are given by way of example and should not be construed in a limitative sense. It is further to be noted that the figures given below are whole numbers which are obtained by rounding up or down the true Weight of various fractions.

The elevator 58 supplies to the destalking machine 4 a continuous stream of whole tobacco leaves at a rate of 6,800 kilograms per hour. The mass of whole tobacco leaves delivered per hour contains 5,035 kilograms of tobacco leaf laminae and 1,765 kilograms of ribs. The collecting pipe 48 will receive 5,050 kilograms of material which comprises all of the laminae and 15 kilograms of ribs, i.e., about 0.3 percent of ribs. The remainder of the ribs (1,750 kilograms) will constitute waste or will be fed on to a further apparatus for additional processing.

The first destalking machine 4 breaks up whole tobacco leaves into laminae and ribs which form with such laminae a primary mixture containing 4,400 kilograms of free laminae and 2,400 kilograms of lighter and heavier ribs and fragments of laminae which continue to adhere to certain ribs. This primary mixture is discharged through the hopper 60 and is conveyed via duct 62 to enter the first separator 6. The latter segregates 2,850 kilograms of pure laminae which are conveyed into the collecting pipe 48 via branches 56 and outlet 34. The remaining portion of the primary mixture containing 2,400 kilograms of lighter and heavier ribs and 1,550 kilograms of separated laminae is discharged into the hopper 76 and passed through the duct 82 on its way into the second separator 8 which segregates 1,000 kilograms of laminae. The secondary mixture leaving the separator 8 via hopper 78 contains a very strong concentration of ribs (2,400 kilograms) and 550 kilograms of free laminae. The duct 84 conveys this secondary mixture into the secondary separator 10 which is shorter than the separators 6, 8 because its efliciency is only half of that of the separators 6, 8. In accordance with a feature of my invention, the separator 10 is adjusted in such a way that it segregates from the secondary mixture 550 kilograms of material constituting a third mixture and consisting of 500 kilograms of heavy (large) laminae and 50 kilograms of lighter ribs. The conveyor 32 receives the remainder of the secondary stream (2,350 kilograms of ribs and 50 kilograms of free laminae) which is admitted into the elevator 64. The latter also receives the heavier fraction (50 kilograms) of the third stream which is segregated from the lighter fraction in the additional separator 28. The outlet 26 delivers the third mixture to the air lock 50 whose pipe 52 delivers it to the rapidly advancing belt 54 which latter delivers the third mixture into the inlet of the additional separator 28. The material issuing from the outlet of the additional separator 28 comprises the heavier fraction kilograms of lighter ribs) and 50 kilograms of laminae, i.e., the outlet 38 delivers into the collecting pipe 450 kilograms of laminae and the outlet 30 delivers to the belt 32 a mass of comminuted tobacco weighing 100 kilograms and consisting of equal percentages of laminae and lighter ribs. This mass constitutes the remainder of the third mixture and is intermingled with the remainder of the secondary mixture (on the belt 32) to form therewith a fourth mixture entering the destalking machine 12. The machine receives 2,500 kilograms of material and separates from the ribs additional laminae weighing 350 kilograms so that the mixture leaving the machine 12 via hopper 68 contains 450 kilograms of free laminae and 2,050 kilograms of ribs some of which still carry fragments of laminae. The duct admits such mixture into the separator 14 which segregates 300 kilograms of laminae passing through the outlet 40 and into the collecting pipe 48. The remainder consists of 150 kilograms of laminae and 2,050 kilograms of lighter and heavier ribs carrying fragments of laminae. Such remainder is discharged via hopper and passes through the duct 86 to enter the separator 16 which segregates kilograms of laminae entering the outlet 42 for admission into the pipe '48. The hopper of the separator 16 receives 2,050 kilograms of ribs and 50 kilograms of free laminae and discharges such material onto the elevator 66 for admission into the destalking machine 18 which segregates from the ribs 200 kilograms of laminae so that the hopper 72 receives a mixture containing 1850 kilograms of ribs with fragments of laminae and 250 kilograms of free laminae. The hopper 72 admits this mixture into the duct 74 for introduction into the separator 20 which segregates 200 kilograms of laminae for admission into the pipe 48 via outlet 44. The remainder consisting of 1850 kilograms of ribs with fragments of laminae and 50 kilograms of free laminae is discharged onto the belt 88 for admission into the destalking machine 22 which separates from ribs the remaining 100 kilograms of laminae so that the last separator 24 receives i750 kilograms of lighter and heavier ribs and kilograms of free laminae. This separator 24 segregates the free laminae (150 kilograms) and delivers them into the pipe 48 via outlet 46. The belt 92 receives 1,750 kilograms of ribs and feeds them to a pneumatic conveyor duct (not shown) for delivery to the next processing station.

The pipe 48 receives 5,050 kilograms of material including 5,035 kilograms of pure leaf laminae and 15 kilograms of ribs. Thus, the material in the pipe 48 contains a surprisingly high percentage of large laminae. This is due to the fact that the first stage of the apparatus separates about 87 percent of all laminae and that 97 percent of the thus separated laminae are admitted into the pipes 48 through the outlets 34, 36, 38 of the first stage. The shredding teeth and the bars in the basket of the destalking machine 4 are preferably placed at a greater than normal distance from each other to insure that the primary mixture entering the separator 6 contains a higher than normal percentage of large laminae. This is possible because the first stage can segregate a very high percentage of laminae.

The construction of the apparatus shown in FIG. 2 is analogous to that of the apparatus shown in FIGS. 3a-4b. The main difference between the two apparatus is that the one shown in FIG. 2 may comprise one or more additional separators 128 which can replace or are provided in addition to the separator 28 of FIGS. 1, 3a and 4a.

Without further analysis, the foregoing Will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. A method of separating tobacco leaf laminae from tobacco ribs, comprising the steps of destalking tobacco leaves to form a primary mixture containing free laminae and lighter and heavier ribs; separating from the primary mixture the major percentage of laminae whereby the remainder of the primary mixture forms a secondary mixture containing a relatively high concentration of ribs and the remaining free laminae; separating from the secondary mixture at least the major percentage of free laminae and at least some ribs to form a third mixture; separating free laminae from the third mixture; and mixing the remainder of the secondary and third mixtures to form a fourth mixture.

2. A method as set forth in claim 1, wherein said third mixture contains free laminae and lighter ribs.

3. A method as set forth in claim 1, wherein at least some of the ribs in said primary mixture carry fragments of laminae, and further comprising the steps of destalking the ribs in said fourth mixture to bodily separate such ribs from fragments of laminae, and segregating such fragments from the ribs.

4. A method as set forth in claim 1, wherein the free laminae are segregated from the primary stream in a series of segregating operations, and further comprising the step of destalking the ribs in said fourth mixture to bodily separate therefrom at least some fragments of laminae which continue to adhere to such ribs upon completed formation of said primary mixture.

5. A method as set forth in claim 1, wherein said third mixture contains a relatively high percentage of free laminae and a relatively low percentage of lighter ribs.

6. A method as set forth in claim 1, wherein said third mixture is formed by conveying said secondary mixture with a current of an ascending gaseous carrier which entrains free laminae and lighter ribs but is too weak to entrain heavier ribs.

7. In an apparatus for separating tobacco leaf laminae from tobacco ribs, destalking means for breaking up tobacco leaves into a primary mixture consisting of free laminae and lighter and heavier ribs; first separator means for segregating from such primary mixture the major percentage of free laminae, the remainder of the primary mixture forming a secondary mixture which contains remaining free laminae and lighter and heavier ribs; secondary separator means for segregating from the secondary mixture a third mixture containing free laminae intermingled with some of the ribs; and additional separator means positioned to receive the third mixture for segregating free laminae from said third mixture.

8. A structure as set forth in claim 7, wherein said destalking means is arranged to break up tobacco leaves into a primary mixture in which at least some ribs still carry fragments of laminae, and further comprising further destalking means for bodily separating such fragments from the ribs in said fourth mixture and for converting the fourth mixture into a fifth mixture, and further separator means for segregating free laminae from the fifth mixture.

9. A structure as set forth in claim 7, wherein said first separator means comprises a series of individual separators.

10. A structure as set forth in claim 9, wherein said additional separator means discharges the remainder of said third mixture into the remainder of the secondary mixture issuing from said secondary separator means whereby such remainders form a fourth mixture wherein R lets for the remainders of said secondary and third mixtures and wherein the outlet of said additional separator means is located at a level above the outlet of said secondary separator means.

12. A structure as set forth in claim 7, wherein said additional separator'means comprises a pneumatic separator having an inlet for said third mixture, and further comprising mechanical conveyor means for supplying the third mixture into said inlet and an air lock for feeding the third mixture from said secondary separator means to said mechanical conveyor means.

13. A structure as set forth in claim 12, wherein said mechanical conveyor means comprises a rapidly travelling endless belt.

References Cited UNITED STATES PATENTS 3,010,576 11/1961 Harte et al. 209-35 3,200,947 8/ 1965 Wochnowski 209-133 3,310,059 3/1967 Grinzinger 131146 ALDRICH F. MEDBERY, Primary Examiner. 

